menA过表达菌株构建及两阶段pH控制促进VK₂合成

Enhance Vitamin K2 Production Via menA Gene Overexpression and a Two-Stage pH Control Strategy

DOI：10.3969/j.issn.1673-1689.2019.12.005

中文关键词: 纳豆芽孢杆菌 过表达 控制策略 pH 维生素K2

英文关键词: Bacillus subtilisnatto,overexpression,control strategy,pH,vitamin K2

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中文摘要:

为提高纳豆芽孢杆菌合成维生素K₂的能力，构建了纳豆芽孢杆菌体内维生素K₂合成途径中的关键酶—1，4-二羟基-2-萘甲酸-聚异戊二烯转移酶（MenA）—过表达菌株，并在5 L发酵罐水平考察了不同pH对该过表达菌株生长和维生素K2合成能力的影响。结果表明：menA基因的过量表达能使Bacillus subtilis natto维生素K₂合成量提高51%。单一恒定的pH不能满足既能使菌株生长充分，又能最大化产物合成的条件。通过分析不同pH下发酵过程曲线和动力学参数，提出了两阶段pH控制策略：即在发酵前期0~40 h控制pH 7.0，发酵后期40~80 h控制pH 4.0，菌体生物量和维生素K₂合成量分别达到了（11.46±0.67） g/L和（63.60±1.81） mg/L，是原始菌分批发酵pH自然状态下的1.5倍和2.6倍。

英文摘要:

To improve vitamin K2 production，1，4-dihydroxy-2-naphthoicacid polyprenyltransferase （MenA）which was a key enzyme for vitamin K₂synthesis inBacillus subtilisnatto was overexpressed. The effects of pH on cell growth and vitamin K2 production was also investigated in a 5 L fermentator. It was shown that the vitamin K₂production was enhanced by 51% when menA gene was overexpressed. The mono-control of pH could not balance the cell growth and vitamin K₂production. A two-stage pH control strategy was employed，i.e. pH was controlled at 7.0 between 0~40 h and switched to 4.0 between 40~80 h. The biomass and vitamin K₂production reached（11.46±0.67）g/L and（63.60±1.81） mg/L，which were 1.5 and 2.6 times of that of pH uncontrolled condition by original strain，respectively.

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